Method and apparatus for detecting location changes and monitoring assistance data via scanning

ABSTRACT

Example methods, apparatuses, or articles of manufacture are disclosed herein that may be utilized, in whole or in part, to facilitate or support one or more operations or techniques for detecting location changes and monitoring assistance data via scanning for use in or with a mobile device. Briefly, in accordance with at least one implementation, a method may include obtaining, at a mobile device, a rough estimate of a location of the mobile device; identifying a plurality of transmitters within a signal acquisition range of the roughly estimated location; transmitting probe requests addressed to at least some of the transmitters; and selectively initiating a passive scan at a receiver of the mobile device if a number of responses to the probe requests received from the transmitters is less than a threshold number.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent Application is a continuation of U.S. patent applicationSer. No. 14/054,602, entitled “METHOD AND APPARATUS FOR DETECTINGLOCATION CHANGES AND MONITORING ASSISTANCE DATA VIA SCANNING”, filedOct. 15 2013, assigned to the assignee hereof, and expresslyincorporated herein by reference in its entirety.

BACKGROUND

1. Field

The present disclosure relates generally to position or locationestimations of mobile communication devices and, more particularly, todetecting location changes and monitoring assistance data via scanningfor use in or with mobile communication devices.

2. Information

Mobile communication devices, such as, for example, cellular telephones,portable navigation units, laptop computers, personal digitalassistants, or the like are becoming more common every day. Certainmobile communication devices, such as, for example, location-awarecellular telephones, smart telephones, or the like may assist users inestimating their geographic locations by providing positioningassistance data obtained or gathered from various systems. For example,in an outdoor environment, certain mobile communication devices mayobtain an estimate of their geographic location or so-called “positionfix” by acquiring wireless signals from a satellite positioning system(SPS), such as the global positioning system (GPS) or other like GlobalNavigation Satellite Systems (GNSS), cellular base station, locationbeacon, etc. via a cellular telephone or other wireless communicationsnetwork. In some instances, acquired wireless signals may be processedby or at a mobile communication device, and its location may beestimated using known techniques, such as, for example, Advanced ForwardLink Trilateration (AFLT), base station identification, or the like.

In an indoor environment, at times, certain mobile communication devicesmay be unable to reliably receive or acquire satellite or like wirelesssignals to facilitate or support one or more position estimationtechniques. For example, signals from an SPS or other wirelesstransmitters may be attenuated or otherwise affected in some manner(e.g., insufficient, weak, fragmentary, blocked, etc.), which may atleast partially preclude their use for position estimations. As such, inan indoor environment, different techniques may be employed to enablenavigation or location services. For example, a mobile communicationdevice may obtain a position fix by measuring ranges to three or moreterrestrial wireless access points positioned at known locations. Rangesmay be measured, for example, by obtaining a Media Access Controlidentifier (MAC ID) address from wireless signals received from suitableaccess points and measuring one or more characteristics of receivedsignals, such as signal strength, round trip delay, or the like.

At times, an indoor location of a mobile communication device may beestimated via radio heat map signature matching, for example, in whichcurrent or live characteristics or signatures of wireless signalsreceived at the device are compared with expected or previously measuredsignal characteristics stored as heat map values in a database. In someinstances, however, such as in larger indoor or like environments withmultiple floors, access points, or feasible routes, for example, a radioheat map may be quite voluminous or comprehensive so as to tax availablebandwidth in wireless communication links, memory of a mobilecommunication device, or the like. In addition, downloading or otherwiseaccessing voluminous or comprehensive radio heat maps may, for example,lead to longer latencies or processing times with respect to positionoperations. This may also increase power consumption of certain mobilecommunication devices, such as mobile devices with limited powerresources (e.g., battery-operated, etc.), for example, thus, affectingoperating lifetime or overall utility of such devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive aspects are described with reference tothe following figures, wherein like reference numerals refer to likeparts throughout the various figures unless otherwise specified.

FIG. 1 is a schematic diagram illustrating features associated with animplementation of an example operating environment.

FIG. 2 is a flow diagram illustrating an implementation of an exampleprocess that may be performed to facilitate or support techniques fordetecting location changes and monitoring assistance data via scanning.

FIG. 3 is an illustration of an implementation of an example radio heatmap covering an area of a rough location of a mobile device.

FIG. 4 is a flow diagram illustrating another implementation of anexample process that may be performed to facilitate or supporttechniques for detecting location changes and monitoring assistance datavia scanning.

FIG. 5 is a schematic diagram illustrating an implementation of anexample computing environment associated with a mobile device.

FIG. 6 is a schematic diagram illustrating an implementation of anexample computing environment associated with a server.

SUMMARY

Example implementations relate to techniques for detecting locationchanges and monitoring assistance data via scanning. In oneimplementation, a method may comprise obtaining, at a mobile device, arough estimate of a location of the mobile device; identifying aplurality of transmitters within a signal acquisition range of theroughly estimated location; transmitting probe requests addressed to atleast some of the transmitters; and selectively initiating a passivescan at a receiver of the mobile device if a number of responses to theprobe requests received from the transmitters is less than a thresholdnumber.

In another implementation, an apparatus may comprise a mobile devicecomprising a wireless transceiver to communicate with a wirelessnetwork; and one or more processors programmed with instructions toobtain a rough estimate of a location of the mobile device; identify aplurality of transmitters within a signal acquisition range of theroughly estimated location; transmit probe requests addressed to atleast some of the transmitters; and selectively initiate a passive scanat a receiver of the mobile device if a number of responses to the proberequests received from the transmitters is less than a threshold number.

In yet another implementation, an apparatus may comprise means forobtaining, at a mobile device, a rough estimate of a location of themobile device; means for identifying a plurality of transmitters withina signal acquisition range of the roughly estimated location; means fortransmitting probe requests addressed to at least some of thetransmitters; and means for selectively initiating a passive scan at areceiver of the mobile device if a number of responses to the proberequests received from the transmitters is less than a threshold number.

In yet another implementation, an article may comprise a non-transitorystorage medium having instructions stored thereon executable by aspecial purpose computing platform to obtain, at a mobile device, arough estimate of a location of the mobile device; identify a pluralityof transmitters within a signal acquisition range of the roughlyestimated location; transmit probe requests addressed to at least someof the transmitters; and selectively initiate a passive scan at areceiver of the mobile device if a number of responses to the proberequests received from the transmitters is less than a threshold number.It should be understood, however, that these are merely exampleimplementations, and that claimed subject matter is not limited to theseparticular implementations.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a thorough understanding of claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter may be practiced without these specific details. In otherinstances, methods, apparatuses, or systems that would be known by oneof ordinary skill have not been described in detail so as not to obscureclaimed subject matter.

Some example methods, apparatuses, or articles of manufacture aredisclosed herein that may be implemented, in whole or in part, tofacilitate or support one or more operations or techniques for detectinglocation changes and monitoring assistance data via scanning for use inor with a mobile communication device. As used herein, “mobile device,”“mobile communication device,” “wireless device,” “location-aware mobiledevice,” or the plural form of such terms may be used interchangeablyand may refer to any kind of special purpose computing platform orapparatus that may from time to time have a position or location thatchanges. In some instances, a mobile communication device may, forexample, be capable of communicating with other devices, mobile orotherwise, through wireless transmission or receipt of informationaccording to one or more communication protocols. As a way ofillustration, special purpose mobile communication devices, which mayherein be called simply mobile devices, may include, for example,cellular telephones, smart telephones, personal digital assistants(PDAs), laptop computers, personal entertainment systems, tabletpersonal computers (PC), personal audio or video devices, personalnavigation devices, or the like. It should be appreciated, however, thatthese are merely examples of mobile devices that may be used, at leastin part, to implement one or more operations or techniques for detectinglocation changes and monitoring assistance data via scanning, and thatclaimed subject matter is not limited in this regard. It should also benoted that the terms “position” and “location” may be usedinterchangeably herein.

In this context, a location context identifier (LCI) may refer to alocally defined geographic area that may be used to store or accessgeographically linked information associated with that area, such as,for example, a building, a particular floor of a building, a certainportion or wing of a building, or like areas that may or may not bemapped according to a global coordinate system. As will be seen, one ormore LCIs may be selectively provided to a mobile device as part ofpositioning assistance data and may be used, at least in part, to obtainor improve an indoor position fix of the mobile device, such as inconnection with one or more radio heat maps, for example. Depending onan implementation, one or more LCIs may, for example, be provided ormade available to a mobile device by an indoor navigation system,suitable server, or the like. For example, one or more LCIs may bestored at a location server and may be accessible by a mobile device viaa selection of a Uniform Resource Locator (URL), just to illustrate onepossible implementation.

At times, to detect or discover all or most wireless transmitterslocated within an acquisition range, such as to acquire positioning orlike signals, for example, it may be useful for a mobile device toperform one or more Wi-Fi scans of an indoor or like area of interest.For example, at times, a mobile device may perform an active scan, apassive scan, or any combination thereof. As will be seen, a mobiledevice may implement an active scan of an area via transmitting one ormore probe requests, such as in the form of one or more unicast packets,for example, to one or more known wireless transmitters and receivingone or more probe responses. For example, a mobile device may transmit arequest to send (RTS) to a number of known wireless transmitters withina given area, and wireless transmitters may respond with a clear to send(CTS) probe response. A probe response may include, for example, a basicservice set identification (BSSID) of a probed wireless transmitter,service set identification (SSID) of an associated Wi-Fi-type wirelesscommunications network, or other information that may be used, at leastin part, for localization.

An active scan does not necessarily block data traffic and may take lesstime to complete (e.g., 10 ms per wireless transmitter, etc.). Here, oneor more active measurements with respect to probed wireless transmittersmay, for example, be obtained or collected. For example, in someinstances, such as if a known wireless transmitter emits a relativelyconsistent location-dependent characteristic or exhibits a relativelyconsistent processing delay, respective RSSI or RTT may, for example, beobtained or collected. Thus, the terms “active scan” and “activemeasurements” may be used interchangeably herein. As will be describedin greater detail below, one or more active scans or measurements may beused, at least in part, for more effective or efficient indoorpositioning. An RTS may typically be sent to wireless transmitters withknown MAC addresses and frequency channels, but, at times, however,frequency channels may be unknown. Also, since there may be a relativelylarge number of in-range wireless transmitters, in some instances,overhead of an active scan may be quite high.

Thus, in some instances, such as to obtain frequency channels ofin-range wireless transmitters, for example, a passive scan may beimplemented or performed. Typically, a passive scan may involve“listening” for periodic beacon-type wireless signals communicated byone or more wireless transmitters within an acquisition range of themobile device. Here, knowledge of MAC addresses of scanned wirelesstransmitters may not be required or useful, for example, and a passivescan may detect a wireless transmitter with a hidden service setidentification (SSID). As such, a passive scan may, for example, provideor yield a list of MAC addresses, corresponding operational channels,etc. of all or most wireless transmitters located within an acquisitionrange of a mobile device. A passive scan, however, may take a relativelylonger time to complete (e.g., 3 sec., etc.), for example, and maypreclude a mobile device from transmitting or receiving data trafficduring the scan. As such, at times, a passive scan may be moreenergy-consuming, power or bandwidth-expensive, etc., such as inrelation to an active scan, for example. Of course, these are merelyexamples relating to passive or active scans, and claimed subject matteris not so limited.

As was indicated, in some instances, positioning assistance data maycomprise, for example, an electronic digital map of an indoor or likearea of interest identifiable via one or more LCIs. An electronicdigital map may include, for example, indoor features of an area, suchas doors, hallways, staircases, elevators, walls, etc., as well aspoints of interest, such as restrooms, stores, entry ways, pay phones,or the like. By obtaining a digital map of an indoor or like area ofinterest, such as identified via one or more relevant LCIs, for example,a mobile device may be capable of overlaying its current location overthe displayed map of the area so as to provide an associated user withadditional context, frame of reference, or the like. Of course, theseare merely examples relating to digital maps or LCIs, and claimedsubject matter is not so limited.

At times, positioning assistance data may include, for example, a radioheat map constructed for an indoor or like environment. A radio heat mapmay comprise, for example, radio heat map values representing observedcharacteristics of wireless signals or so-called signal “signatures”indicative of expected signal strength (e.g., RSSI, etc.), round-tripdelay times (e.g., RTT, etc.), or like characteristics at particularlocations in an indoor or like area of interest. A radio heat map may beprovided or made available by a suitable server (e.g., location server,positioning assistance server, etc.), such as for a download via one ormore wireless communications links, for example. A downloaded radio heatmap may be stored or “cached” in a local memory of a mobile device, forexample, to facilitate or support one or more signal signature matchingoperations, as was indicated. A radio heat map may facilitate or supportmeasurements of ranges to one or more wireless transmitters, such as oneor more access points, for example, positioned at known locations withinan indoor or like area of interest. Thus, for a known wirelesstransmitter, a radio heat map may, for example, associate a particularlocation with a heat map value representative of an expected signalsignature (e.g., RSSI, RTT, etc.) at the location. As such, heat mapvalues associated with one or more known wireless transmitters may, forexample, enable a mobile device to correlate observed signal signatureswith locations within an indoor or like area of interest.

As alluded to previously, positioning assistance data (e.g., locationsof wireless transmitters, radio heat maps, digital maps for display,routing graphs, etc.) for a relatively large or multi-story indoor orlike environment may be quite voluminous or comprehensive, which maylead to increased processing times, affect power consumption of a mobiledevice, or the like. For example, at times, there may be uncertainty asto a particular floor (e.g., of a shopping mall, etc.) on which a mobiledevice is located. To resolve this uncertainty, a mobile device maydownload multiple radio heat maps, such as for each candidate floor, forexample. Again, this may be time-consuming, waste network bandwidth,memory or power of a mobile device, or the like. In addition, at times,due, at least in part, to limited memory resources, coverage or metadatatransfer plan, etc., a mobile device may be unable to reliably receiveor download a comprehensive radio heat map into a local memory, forexample. As such, at times, indoor positioning or navigationcapabilities of certain mobile devices may, for example, be less usefulor possibly faulty.

Thus, in some instances, such as in relatively large or multi-storyindoor or like environments, for example, it may be useful to resolve ordetermine a general area (e.g., a particular floor, wing of a building,etc.) of where a mobile device may be located. A mobile device may thenbe provided with smaller, localized positioning assistance data for usein that particular area (e.g., a portion of a heat map, locations ofwireless transmitters located on a particular floor, a digital mapidentified via relevant LCIs, etc.). At times, a mobile device may, forexample, resolve its location as being in a particular portion of aninterior area, particular floor of a building, etc. by acquiring signalsfrom one or more wireless transmitters positioned at known locations.For example, a mobile device may acquire a MAC address or otherinformation modulating a signal transmitted by a wireless transmitter(e.g., an IEEE std. 802.11 access point, etc.) located within anacquisition range of the mobile device. With acquisition of signalstransmitted by a sufficient number of wireless transmitters, a mobiledevice may, for example, infer or determine that its location is withina particular area of a larger indoor or like environment. A mobiledevice may then request or access smaller-sized positioning assistancedata applicable to that particular area, such as via a suitable server,for example.

In some instances, a mobile device may travel within an indoor or likeenvironment, such as within a multi-story shopping mall, for example, byfrequently moving in and out of various areas (e.g., floors, wings,etc.) that may be respectively serviced by localized (e.g., smaller,etc.) segments of available positioning assistance data. Thus, at times,to obtain new positioning assistance data, it may be useful to detect ordiscover all or most in-range wireless transmitters of anewly-encountered area, for example. For this purpose, a mobile devicemay, for example, be “tempted” (e.g., configured, programmed, defaulted,etc.) to implement a passive scan. Unfortunately, repeated use ofpassive scans may consume significant battery or network resources,interrupt cellular or like communications, or the like, as wasindicated. Accordingly, it may be desirable to develop one or moremethods, systems, or apparatuses that may implement more effective orefficient indoor location or navigation techniques, such as byminimizing a number of passive scans via active measurements, forexample, while increasing a number of detected wireless transmittersthat may be used, in whole or in part, for localization.

Thus, as will be described in greater detail below, in animplementation, instead of initiating a passive scan, a mobile devicemay, for example, utilize one or more active measurements (e.g., RSSI,RTT, etc.), such as while probing one or more known wirelesstransmitters. For example, a mobile device may send an RTS to wirelesstransmitters identified to be within a presumed general area of themobile device and whose observed or expected RSSI values are higher thansome predetermined RSSI threshold, just to illustrate one possibleimplementation. If a number of probed wireless transmitters from whichCTS responses are received is greater than some threshold number, amobile device may, for example, infer that its location is within thatpresumed general area. If a number of probed wireless transmitters fromwhich CTS responses are received is less than some threshold number, amobile device may, for example, infer that its location is not or nolonger within that presumed general area. In such a case, a mobiledevice may, among other things, initiate a passive scan, for example. Aswill be seen, at times, a mobile device may also trigger LCI detectionin order to determine whether a location of the mobile device haschanged (e.g., a user has changed floors, etc.). In some instances, suchas if it is determined that a location of a mobile device has changed,for example, new positioning assistance data including an applicableradio heat map or a portion thereof, digital map, etc. may be downloadedand used, at least in part, for localization.

If CTS responses received from a number of probed wireless transmittersare greater than some threshold number, a mobile device may, forexample, infer that its location is within that presumed general area.If CTS responses received from a number of probed wireless transmittersare less than some threshold number, a mobile device may, for example,infer that its location is not or no longer within that presumed generalarea. In such a case, a mobile device may, among other things, initiatea passive scan, for example, triggering LCI detection in order todetermine whether a location of the mobile device has changed (e.g., auser has changed floors, etc.). If so, new positioning assistance dataincluding, for example, an applicable radio heat map or a portionthereof, digital map, etc. may be downloaded and used, at least in part,for localization.

FIG. 1 is a schematic diagram illustrating features associated with animplementation of an example operating environment 100 capable offacilitating or supporting one or more processes or operations fordetecting location changes and monitoring assistance data via scanning.As was indicated, operating environment 100 may be implemented inconnection with one or more radio heat maps for an indoor or likeenvironment that may be employed, in whole or in part, by a mobiledevice 102, for example. It should be appreciated that operatingenvironment 100 is described herein as a non-limiting example that maybe implemented, in whole or in part, in the context of variouscommunications networks or combination of networks, such as publicnetworks (e.g., the Internet, the World Wide Web), private networks(e.g., intranets), wireless local area networks (WLAN, etc.), or thelike. It should also be noted that claimed subject matter is not limitedto indoor implementations. For example, at times, one or more operationsor techniques described herein may be performed, at least in part, in anindoor-like environment, which may include partially or substantiallyenclosed areas, such as urban canyons, town squares, amphitheaters,parking garages, rooftops, patios, or the like. At times, one or moreoperations or techniques described herein may be performed, at least inpart, in an outdoor environment.

As illustrated, operating environment 100 may comprise, for example, oneor more satellites 104, base transceiver stations 106, wirelesstransmitters 108, etc. capable of communicating with mobile device 102via wireless communication links 110 in accordance with one or morecommunication protocols. Satellites 104 may be associated with one ormore satellite positioning systems (SPS), such as, for example, theUnited States Global Positioning System (GPS), the Russian GLONASSsystem, the European Galileo system, as well as any system that mayutilize satellites from a combination of satellite systems, or anysatellite system developed in the future. Base transceiver stations 106,wireless transmitters 108, etc. may be of the same or similar type, forexample, or may represent different types of devices, such as accesspoints, radio beacons, cellular base stations, femtocells, or the like,depending on an implementation. At times, one or more wirelesstransmitters, such as wireless transmitters 108, for example, may becapable of transmitting as well as receiving wireless signals.

Although not shown, in some instances, operating environment 100 may,for example, include a relatively larger number of wireless transmitters108 associated with an indoor or like area of interest. To illustrate,typically, although not necessarily, a larger number of wirelesstransmitters 108, such as access points, femtocells, etc., may, forexample, correspond to or correlate with a more voluminous orcomprehensive radio heat map. As was indicated, at times, this may leadto or result in having relatively large positioning assistance data,which may at least partially preclude position determination, locationor navigation services, affect power consumption, etc. of mobile device102. Of course, these are merely details relating to operatingenvironment 100, and claimed subject matter is not so limited.

In some instances, one or more base transceiver stations 106, wirelesstransmitters 108, etc. may, for example, be operatively coupled to anetwork 112 that may comprise one or more wired or wirelesscommunications or computing networks capable of providing suitableinformation, such as via one or more wireless communication links 114,110, etc. As will be seen, information may include, for example,positioning assistance data, such as a radio heat map, digital map, LCI,identities or locations of one or more base transceiver stations 106,wireless transmitters 108, etc., recent position fix obtained via anSPS, probe request or response, or the like. In an implementation,network 112 may be capable of facilitating or supporting communicationsbetween suitable computing platforms or devices, such as, for example,mobile device 102, one or more base transceiver stations 106, wirelesstransmitters 108, as well as one or more servers associated withoperating environment 100. In some instances, servers may include, forexample, a location server 116, positioning assistance server 118, aswell as one or more other servers, indicated generally at 120 (e.g.,navigation, information, map, etc. server, etc.), capable offacilitating or supporting one or more operations or processesassociated with operating environment 100.

As will be seen, location server 116 may provide a rough estimate of alocation of mobile device 102, such as within an indoor or like area ofinterest, for example, associated with operating environment 100. Arough estimate of a location of mobile device 102 may, for example, bedetermined based, at least in part, on last or a recent position fixobtained via an SPS, input provided by an associated user (e.g., bytyping an address, selecting a name, etc. of shopping mall, etc.),ranges measured to one or more known wireless transmitters, or the like.For example, at times, a rough estimate of a location of mobile device102 may be determined using proximity to one or more reference points,such as by knowing which base transceiver station 106, wirelesstransmitter 108, etc. mobile device 102 is using at a given time. Inaddition, at times, location server 116 may provide an LCI for aparticular indoor or like area of interest, such as in connection withan applicable digital map, for example. As was indicated, an LCI maycomprise, for example, a locally defined area, such as a particularfloor or wing of a building that is not mapped according to a globalcoordinate system. Thus, in some instances, such as at or upon entry ofan indoor or like area of interest, for example, mobile device 102 maycommunicate a request to location server 116 to provide one or more LCIscovering an applicable interior area. Here, a request may reference arough estimate of a location of mobile device 102, such that locationserver 116 may associate the rough location with an area identified byone or more LCIs, for example, and then communicate relevant LCIs tomobile device 102.

In some instances, mobile device 102 may utilize one or more receivedLCIs, in whole or in part, in subsequent messages with a suitableserver, such as server 120, for example, to obtain navigation, map, orother information relevant to an area identified by one or more LCIs(e.g., a digital map, routing graph, etc.). Positioning assistanceserver 118 may, for example, provide positioning assistance data, suchas locations or identities (e.g., MAC addresses, etc.) of wirelesstransmitters, a radio heat map covering an area identified via one ormore LCIs, or the like. It should be noted that even though a certainnumber of computing platforms or devices are illustrated herein, anynumber of suitable computing platforms or devices may be implemented tofacilitate or otherwise support one or more techniques or processesassociated with operating environment 100. For example, at times,network 112 may be coupled to one or more wired or wirelesscommunications networks (e.g., Wi-Fi, etc.) so as to enhance a coveragearea for communications with mobile device 102, one or more basetransceiver stations 106, wireless transmitters 108, servers 116, 118,120, or the like. In some instances, network 112 may facilitate orsupport femtocell-based operative regions of coverage, for example.Again, these are merely example implementations, and claimed subjectmatter is not limited in this regard.

With this in mind, attention is now drawn to FIG. 2, which is a flowdiagram illustrating an implementation of an example process 200 thatmay be performed, in whole or in part, to facilitate or support one ormore operations or techniques for detecting location changes andmonitoring assistance data via scanning for use in or with a mobiledevice, such as mobile device 102 of FIG. 1, for example. It should benoted that information acquired or produced, such as, for example, inputsignals, output signals, operations, results, etc. associated withexample process 200 may be represented via one or more digital signals.It should also be appreciated that even though one or more operationsare illustrated or described concurrently or with respect to a certainsequence, other sequences or concurrent operations may be employed. Inaddition, although the description below references particular aspectsor features illustrated in certain other figures, one or more operationsmay be performed with other aspects or features.

Example process 200 may, for example, begin at operation 202 withobtaining, at a mobile device, a rough estimate of a location of themobile device. As was indicated, a rough estimate of a location of amobile device may, for example, be obtained via a recent position fixobtained from an SPS, user input, proximity to one or more referencepoints, measured ranges to one or more wireless transmitters, or thelike. At operation 204, a plurality of transmitters may, for example, beidentified within a signal acquisition range of the roughly estimatedlocation. For example, at times, a plurality of transmitters may beidentified via a radio heat map covering an area of a rough location ofa mobile device, via a previously performed Wi-Fi scan (e.g., passive,active, etc.), relevant LCI, cached routability graph, or the like. Insome instances, one or more of a plurality of transmitters may comprise,for example, fixed location transmitters (e.g., one or more transmittershaving a fixed reference point, etc.), just to illustrate anotherpossible implementation.

With regard to operation 206, having identified a plurality oftransmitters, a mobile device may, for example, transmit a number ofprobe requests (e.g., RTS, etc.) addressed to at least some of thesetransmitters. For example, in some instances, a mobile device mayaddress probe requests to transmitters whose one or more expected signalcharacteristics (e.g., RSSI, RTT, etc.) exceed some predeterminedthreshold value. Here, one or more active measurements regarding theseone or more expected signal characteristics, for example, may beutilized, at least in part, as previously discussed.

For example, as illustrated in FIG. 3, a number of proximatetransmitters, referenced A through J, whose expected RSSI values exceedsome predetermined threshold value may be selected, such as via a radioheat map 300 covering an area of a rough location 302 of a mobiledevice. Here, for purposes of illustration, each shaded area 304 mayrespectively correspond to or represent a radio signal distribution orrange of interest of transmitters A-J, for example. As was indicated, inat least one implementation, a range of interest may comprise, forexample, a range where expected RSSI values are higher than a certainpredetermined RSSI threshold value. An RSSI threshold value may bedetermined, at least in part, experimentally and may be pre-defined orconfigured, for example, or otherwise dynamically defined in somemanner, depending on a particular application, environment, transmitter,or the like. By way of example but not limitation, in one particularsimulation or experiment, it appeared that an RSSI threshold value ofabout −90 dBm (minus 90 decibels of power with reference to onemiliwatt) may prove beneficial in selecting known transmitters to beprobed. Of course, details relating to a radio heat map or RSSIthreshold value are merely examples to which claimed subject matter isnot limited. For example, as was indicated, in some instances, such asif a plurality of known transmitters positioned within an area ofinterest exhibit relatively consistent processing delays, respective RTTmeasurements may be utilized, at least in part.

Thus, as illustrated in FIG. 3, at times, it may be determined that amobile device is located within ranges of some transmitters whoseexpected RSSI values exceed a predetermined RSSI threshold value, suchas transmitters A, B, and C, for example. Accordingly, here, a mobiledevice may, for example, transmit a number of probe requests addressedto these transmitters. As also illustrated, at times, ranges 304 ofproximate transmitters, such as transmitters A through J, for example,may not be isotropic due, at least in part, to radio propagation ormultipath effects (e.g., wall fading or shadowing, floor reflection,etc.) within an indoor or like environment covered by radio heat map300. Of course, these are merely examples relating to transmitters orranges, and claimed subject matter is not so limited.

Referring back to process 200 of FIG. 2, at operation 208, a passivescan may be selectively initiated, such as at a receiver of a mobiledevice, for example, if a number of responses to probe requests receivedfrom the transmitters (e.g., transmitters A, B, and C of FIG. 3, etc.)comprise less than a threshold number. For example, in certainsimulations or experiments, it has been observed that if a locationtransmitter selected to be probed has not responded, a few particular orrelevant events may have occurred. More specifically, non-responsivenessof a probed location transmitter may be indicative of an associated userchanging floors, for example, in which case it may be useful todetermine and provide a relevant LCI using one or more appropriatetechniques.

Here, one or more LCI disambiguation (LCI-D) techniques may, forexample, be employed, in whole or in part. For example, a mobile deviceor suitable server may disambiguate or distinguish between or among anumber of candidate LCIs covering a rough location of the mobile devicebased, at least in part, on one or more wireless signals that the mobiledevice is receiving at a given time, just to illustrate one possibleimplementation. Thus, if a mobile device is receiving a wireless signalfrom a location transmitter associated with a particular LCI, forexample, that LCI may be provided to the mobile device. If a mobiledevice is receiving wireless signals from a plurality of transmittersassociated with multiple LCIs, at times, image features extracted fromcaptured images corresponding to particular LCIs may, for example, beused, at least in part, to disambiguate between candidate LCIs. Ofcourse, these are merely examples relating to LCI-D techniques, andclaimed subject matter is not so limited.

In some instances, it has also been observed that non-responsiveness ofa probed location transmitter may, for example, indicate that thetransmitter may have been turned off, removed, or relocated to anotherarea, in which case it may be useful to ignore the non-responsivetransmitter. Also, at times, non-responsiveness of a locationtransmitter may be indicative of a change in radio propagation channelsof an indoor or like environment, for example, which may requireregeneration or reconstruction of applicable positioning assistancedata. Thus, in some instances, probe requests implemented in connectionwith one or more active measurements may, for example, help to determinea particular reason for non-responsiveness of a probed locationtransmitter, which may provide benefits, as will be seen.

Continuing with the above discussion, if, upon performing activemeasurements with respect to selected transmitters within a particulararea, for example, no response is received from N of them, where N isgreater than a certain threshold number N₀, then it may be assumed thattransmitter-related knowledge is insufficient for additional activemeasurements within that area. In such a case, it may be useful toinitiate a passive scan, such as to determine a cause fornon-responsiveness of transmitters, for example. Likewise, here, athreshold number _(N0) may be determined, at least in part,experimentally and may be pre-defined or configured, for example, orotherwise dynamically defined in some manner, depending on a particularapplication, environment, transmitter, or the like.

In some instances, it may also be useful to implement one or moreprocesses, such as in connection with a passive scan of operation 208,for example, to improve or enhance location determination of a mobiledevice, such as using one or more appropriate techniques. By way ofexample but not limitation, one or more processes that may beimplemented, in whole or in part, in connection with a passive scan mayinclude those listed below, though claimed subject matter is not solimited.

For example, here, a process implementing a detection of a new LCI maybe triggered, such as using results of a passive scan to check whether auser of an associated mobile device has changed areas (e.g., floors,wings, etc.). If so, new or applicable positioning assistance dataincluding a new LCI may, for example, be provided or downloaded to amobile device. Detection of a new LCI may, for example, be performed viaone or more LCI-D techniques, such as discussed above. At times, here, asingle point fix process may, for example, be performed using one ormore measurements obtained during a passive scan or one or more activemeasurements (e.g., subsequent, etc.). Depending on an implementation,measurements may comprise, for example, RSSI measurements, RTTmeasurements, or the like, as was indicated. Single point fix may, forexample, be implemented using any suitable single point fix positioningsolutions or techniques. Also, here, a suitable particle filter may, forexample, be restarted, such as at or by a mobile device, suitableserver, or any combination thereof. Particle filters are generally knownand need not be described here in greater detail. In addition, here, anew set of in-range transmitters may, for example, be extracted orderived, such as via a suitable process, from positioning assistancedata (e.g., a heat map, digital map, etc.) using a newly-estimatedlocation, just to illustrate one possible implementation.

In some instances, such as if one or more newly-extracted or derivedtransmitters are non-responsive, here, an appropriate enterprisemanagement system servicing these transmitters may, for example, bequeried or contacted, such as via a suitable process, so as to determinewhether these transmitters are in-service (e.g., turned off, etc.). Ifone or more non-responsive transmitters are not in service (e.g., turnedoff, etc.), for example, their respective positioning assistance datamay be flagged in a suitable manner and may be ignored until thetransmitters are put back in service (e.g., turned back on, etc.).Otherwise, it may be inferred, for example, that non-responsivetransmitters have been removed, relocated to another area, etc. or thatenvironmental dynamics have changed. In such a case, regeneration orreconstruction of positioning assistance data may, for example, berequested.

Continuing with the above example, if a number of non-responsivetransmitters N is less than a certain threshold number N₀, for example,at times, a passive scan may not be needed or otherwise useful. Thus, amobile device may report one or more non-responsive transmitters to asuitable server, such as for further monitoring, for example. A suitableserver may collect or maintain a list of non-responsive transmitters,and may check status (e.g., periodically, etc.) of transmitters that arerelatively frequently non-responsive, such as, for example, bycontacting an enterprise management server, as was indicated. Optionallyor alternatively, information of non-responsive transmitters (e.g., MACaddresses, locations, etc.) may be removed from positioning assistancedata for a particular indoor or like area of interest.

FIG. 4 is a flow diagram illustrating an implementation of an exampleprocess 400 that may be performed, in whole or in part, to facilitate orsupport one or more operations or techniques for detecting locationchanges and monitoring assistance data via scanning of an area with aplurality of suitable wireless transmitters, such as IEEE std. 802.11access points, for example. Again, here, information acquired orproduced, such as, for example, input signals, output signals,operations, results, etc. associated with example process 400 may berepresented via one or more digital signals. Likewise, even though oneor more operations are illustrated or described concurrently or withrespect to a certain sequence, other sequences or concurrent operationsmay be employed. Also, the description below may reference particularaspects or features illustrated in certain other figures, for example,and one or more operations may be performed with other aspects orfeatures.

Example process 400 may, for example, start at operation 402, wherein arough estimate of a location of a mobile device or any other suitableinformation (e.g., a digital map, routing graph, etc.) facilitating orsupporting example process 400 may be requested or obtained. Atoperation 404, one or more in-range access points may be derived orextracted, such as from an applicable radio heat map, for example. Aswas indicated, here, one or more active measurements may, for example,be used, in whole or in part. For example, from an applicable radio heatmap, a number of in-range access points whose expected RSSI is higherthan a predetermined threshold may be selected, just to illustrate onepossible implementation. With regard to operation 406, a number ofselected in-range access points may be probed, such as via performing anactive scan of an associated indoor or like area if interest, forexample.

At operation 408, a determination may, for example, be made regarding anumber of non-responsive access points, as was discussed. If it isdetermined that a number of non-responsive access points exceeds somepredetermined threshold number, at operation 410, non-responsive accesspoints may, for example, be reported to a suitable server (e.g., forfurther monitoring, etc.). With regard to operation 412, one or morelocalization processes may, for example, be implemented with respect toa mobile device of interest. In some instances, here, a particle filtermay be employed, at least in part, as one possible example. As was alsoindicated, a list of non-responsive access points may be collected ormaintained in some manner (e.g., on a suitable server, mobile device,etc.), for example, and their status may be checked or determined viacontacting an appropriate enterprise management server. Informationregarding one or more non-responsive access points may, for example, beremoved from applicable positioning assistance data (e.g., a radio heatmap, etc.), if desired. Having performed suitable localization, process400 may, for example, be terminated in some manner, such as at operation414.

On the other hand, if it is determined that a number of non-responsiveaccess points is greater than a threshold number, example process 400may, for example, proceed to operation 416, at which point a passivescan may be performed. As was discussed, in some instances, a passivescan may trigger LCI detection, such as using passive scan results, forexample, and an LCI-D may be performed, as indicated at operation 418,so as to detect whether an area has changed (e.g., a user has changedfloors, wings, etc.), such as using one or more techniques discussedabove. At operation 420, if it is determined that an area has changed,new positioning assistance data, such as identified via one or morerelevant LCIs, for example, may be provided to a mobile device, and apassive scan or single point fix may be subsequently performed, such asat operation 424. If an area has not changed, however, a passive scan orsingle point fix may be performed without obtaining new positioningassistance data, as illustrated via an arrow from operation 420 tooperation 424.

With regard to operation 426, a number of in-range access points (e.g.,a new set, etc.) may, for example, be extracted from an applicable radioheat map using a newly estimated (e.g., via relevant LCIs, etc.)location, such as similarly to operation 404, for example. Likewise, atoperation 428, an active scan of in-range access points may, forexample, be performed. If, at operation 430, it is determined that anumber of non-responsive access points exceeding a threshold numberstill remains, example process 400 may proceed to operation 436, and anindoor or like environment (e.g., a venue, etc.) may be flagged, such asfor positioning assistance data regeneration or reconstruction, aspreviously discussed. Subsequently, example process 400 may beterminated, such as at operation 438, for example. If, on the otherhand, it is determined that a number of non-responsive access points isless than a threshold number, at operation 432, a suitable localizationoperation may, for example, be performed, such as via restarting aparticle filter or the like. Here, having obtained a position fix of amobile device, at times, updated positioning assistance data may, forexample, be requested or obtained so as to improve or enhance an indoorlocation of the device (e.g., in a new area, etc.). As illustrated,example process 400 may, for example, be terminated at operation 434 inany suitable manner.

Accordingly, as discussed herein, one or more operations or techniquesfor detecting location changes and monitoring assistance data viascanning may provide benefits. For example, non-responsiveness of one ormore in-range wireless transmitters may be meaningfully analyzed so asto determine whether a location of a mobile device in an areaidentifiable via one or more LCIs has changed (e.g., if an associateduser has traveled to another floor, wing, etc.). It may also allow formore effective or efficient determination of whether one or morein-range wireless transmitters may be relied upon for sufficientlocalization, such as, for example, by inferring whether transmittershave been turned off, taken out of service, moved or relocated toanother area, or the like. Also, knowledge with respect to changes inenvironmental dynamics within an indoor or like area of interest may beadvantageous, since it may provide insights on whether or when it may benecessary or useful to regenerate or reconstruct applicable positioningassistance data, for example.

Another benefit may be that one or more non-responsive in-range wirelesstransmitters may be sufficiently evaluated with a minimal or otherwisereduced utilization of passive scans, for example, such as if certaindiscrepancies are observed in response to one or more active scans. Thismay improve power consumption, memory, operating lifetime, or overallutility of a mobile device, as was indicated. Also, relatively fastdiscovery or detection of an area or LCI change may, for example,positively affect associated user experience, location or navigationservices, or the like. Monitoring or promptly removing one or morenon-responsive in-range wireless transmitters, timely updates ofpositioning assistance data, such as if changes in an environment aredetected, for example, may also prove beneficial in keeping a suitablelocalization process or engine more accurate or reliable. Of course,such a description of certain aspects of one or more operations ortechniques for detecting location changes and monitoring assistance datavia scanning and its benefits is merely an example, and claimed subjectmatter is not so limited.

FIG. 5 is a schematic diagram of an implementation of an examplecomputing environment associated with a mobile device that may be used,at least in part, to facilitate or support one or more operations ortechniques for detecting location changes and monitoring assistance datavia scanning, such as for more effective or efficient positioning in anindoor or like environment. An example computing environment maycomprise, for example, a mobile device 500 that may include one or morefeatures or aspects of mobile device 102 of FIG. 1, though claimedsubject matter is not so limited. For example, in some instances, mobiledevice 500 may comprise a wireless transceiver 502 capable oftransmitting or receiving wireless signals, referenced generally at 504,such as via an antenna 506 over a suitable wireless communicationsnetwork. Wireless transceiver 502 may, for example, be coupled orconnected to a bus 508 via a wireless transceiver bus interface 510.Depending on an implementation, at times, wireless transceiver businterface 510 may, for example, be at least partially integrated withwireless transceiver 502. Some implementations may include multiplewireless transceivers 502 or antennas 506 so as to enable transmittingor receiving signals according to a corresponding multiple wirelesscommunication standards such as Wireless Fidelity (WiFi), Code DivisionMultiple Access (CDMA), Wideband-CDMA (W-CDMA), Long Term Evolution(LTE), Bluetooth®, just to name a few examples.

In an implementation, mobile device 500 may, for example, comprise anSPS or like receiver 512 capable of receiving or acquiring one or moreSPS or other suitable wireless signals 514, such as via an SPS or likeantenna 516. SPS receiver 512 may process, in whole or in part, one ormore acquired SPS signals 514 for estimating a location, rough orotherwise, of mobile device 500. In some instances, one or moregeneral-purpose application processors 518, memory 520, digital signalprocessor(s) (DSP) 522, or like specialized devices or processors notshown may be utilized to process acquired SPS signals 514, in whole orin part, calculate a location of mobile device 500, such as inconjunction with SPS receiver 512, or the like. Storage of SPS or othersignals for implementing one or more positioning operations, such as inconnection with one or more techniques for detecting location changesand monitoring assistance data via scanning, for example, may beperformed, at least in part, in memory 520, suitable registers orbuffers (not shown). Although not shown, it should be appreciated thatin at least one implementation one or more processors 518, memory 520,DSPs 522, or like specialized devices or processors may comprise one ormore processing modules capable of obtaining a rough estimate of alocation of a mobile device; identifying a plurality of transmitterswithin a signal acquisition range of the roughly estimated location;transmitting probe requests addressed to at least some of thetransmitters; and selectively initiating a passive scan at a receiver ofthe mobile device if responses to the probe requests received from anumber of the transmitters comprise less than a threshold number. Itshould also be noted that all or part of one or more processing modulesmay be implemented using or otherwise including hardware, firmware,software, or any combination thereof.

As illustrated, DSP 522 may be coupled or connected to processor 518 andmemory 520 via bus 508. Although not shown, in some instances, bus 508may comprise one or more bus interfaces that may be integrated with oneor more applicable components of mobile device 500, such as DSP 522,processor 518, memory 520, or the like. In various embodiments, one ormore operations or functions described herein may be performed inresponse to execution of one or more machine-readable instructionsstored in memory 520, such as on a computer-readable storage medium,such as RAM, ROM, FLASH, disc drive, etc., just to name a few examples.Instructions may, for example, be executable via processor 518, one ormore specialized processors not shown, DSP 522, or the like. Memory 520may comprise a non-transitory processor-readable memory,computer-readable memory, etc. that may store software code (e.g.,programming code, instructions, etc.) that may be executable byprocessor 518, DSP 522, or the like to perform operations or functionsdescribed herein.

Mobile device 500 may comprise a user interface 524, which may includeany one of several devices such as, for example, a speaker, microphone,display device, vibration device, keyboard, touch screen, etc., just toname a few examples. In at least one implementation, user interface 524may enable a user to interact with one or more applications hosted onmobile device 500. For example, one or more devices of user interface524 may store analog or digital signals on memory 520 to be furtherprocessed by DSP 522, processor 518, etc. in response to input or actionfrom a user. Similarly, one or more applications hosted on mobile device500 may store analog or digital signals in memory 520 to present anoutput signal to a user. In some implementations, mobile device 500 mayoptionally include a dedicated audio input/output (I/O) device 526comprising, for example, a dedicated speaker, microphone, digital toanalog circuitry, analog to digital circuitry, amplifiers, gain control,or the like. It should be understood, however, that this is merely anexample of how audio I/O device 526 may be implemented, and that claimedsubject matter is not limited in this respect. As seen, mobile device500 may comprise one or more touch sensors 528 responsive to touching orlike pressure applied on a keyboard, touch screen, or the like.

In an implementation, mobile device 500 may comprise, for example, acamera 530, dedicated or otherwise, such as for capturing still ormoving imagery, facilitating one or more LCI-D techniques, or the like.Camera 530 may comprise, for example, a camera sensor or like imagingdevice (e.g., charge coupled device, complementary metal oxidesemiconductor (CMOS)-type imager, etc.), lens, analog to digitalcircuitry, frame buffers, etc., just to name a few examples. In someinstances, additional processing, conditioning, encoding, or compressionof signals representing one or more captured images may, for example, beperformed, at least in part, at processor 518, DSP 522, or the like.Optionally or alternatively, a video processor 532, dedicated orotherwise, may perform conditioning, encoding, compression, ormanipulation of signals representing one or more captured images.Additionally, video processor 532 may, for example, decode or decompressone or more stored images for presentation on a display (not shown) ofmobile device 500.

Mobile device 500 may comprise one or more sensors 534 coupled orconnected to bus 508, such as, for example, one or more inertialsensors, ambient environment sensors, or the like. Inertial sensors ofsensors 534 may comprise, for example, one or more accelerometers (e.g.,collectively responding to acceleration of mobile device 500 in one,two, or three dimensions, etc.), gyroscopes or magnetometers (e.g., tosupport one or more compass or like applications, etc.), etc., just toillustrate a few examples. Ambient environment sensors of mobile device500 may comprise, for example, one or more temperature sensors,barometric pressure sensors, ambient light detectors, camera sensors,microphones, etc., just to name few examples. Sensors 534 may generateanalog or digital signals that may be stored in memory 520 and may beprocessed by DSP 522, processor 518, etc., such as in support of one ormore applications directed to positioning or navigation operations,communications, gaming or the like.

In a particular implementation, mobile device 500 may comprise a modemprocessor 536, dedicated or otherwise, capable of performing basebandprocessing of signals received or downconverted via wireless transceiver502, SPS receiver 512, or the like. Similarly, modem processor 536 mayperform baseband processing of signals to be upconverted fortransmission via wireless transceiver 502, for example. In alternativeimplementations, instead of having a dedicated modem processor, basebandprocessing may be performed, at least in part, by processor 518, DSP522, or the like. In addition, in some instances, an interface 538,although illustrated as a separate component, may be integrated, inwhole or in part, with one or more applicable components of mobiledevice 500, such as bus 508 or SPS receiver 512, for example. Optionallyor alternatively, SPS receiver 512 may be coupled or connected to bus508 directly. It should be understood, however, that these are merelyexamples of components or structures that may perform basebandprocessing, and that claimed subject matter is not limited in thisregard.

FIG. 6 is a schematic diagram illustrating an implementation of anexample computing environment or system 600 that may be associated withor include one or more servers or other devices capable of partially orsubstantially implementing or supporting one or more operations ortechniques for detecting location changes and monitoring assistance datavia scanning, such as for more effective or efficient positioning in anindoor or like environment, such as discussed above in connection withFIG. 1, for example. Computing environment 600 may include, for example,a first device 602, a second device 604, a third device 606, etc., whichmay be operatively coupled together via a communications network 608. Insome instances, first device 602 may comprise a server capable ofproviding positioning assistance data, such as, for example, identitiesor locations of known wireless transmitters, radio heat map, proberequest or response, base station almanac, digital map, LCI, or thelike. For example, first device 602 may also comprise a server capableof providing an LCI to a requesting mobile device based, at least inpart, on a rough estimate of a location of the mobile device. Firstdevice 602 may also comprise a server capable of providing indoorpositioning assistance data relevant to a location of an LCI specifiedin a request from a mobile device. Second device 604 or third device 606may comprise, for example, mobile devices, just to illustrate onepossible implementation. In addition, communications network 608 maycomprise one or more wireless transmitters, such as access points,femtocells, or the like. Of course, claimed subject matter is notlimited in scope in these respects.

First device 602, second device 604, or third device 606 may berepresentative of any device, appliance, platform, or machine that maybe capable of exchanging information over communications network 608. Byway of example but not limitation, any of first device 602, seconddevice 604, or third device 606 may include: one or more computingdevices or platforms, such as, for example, a desktop computer, a laptopcomputer, a workstation, a server device, or the like; one or morepersonal computing or communication devices or appliances, such as, forexample, a personal digital assistant, mobile communication device, orthe like; a computing system or associated service provider capability,such as, for example, a database or information storage serviceprovider/system, a network service provider/system, an Internet orintranet service provider/system, a portal or search engine serviceprovider/system, a wireless communication service provider/system; orany combination thereof. Any of first, second, or third devices 602,604, and 606, respectively, may comprise one or more of a mobile device,wireless transmitter or receiver, server, etc. in accordance withexample implementations described herein.

In an implementation, communications network 608 may be representativeof one or more communication links, processes, or resources capable ofsupporting an exchange of information between at least two of firstdevice 602, second device 604, or third device 606. By way of examplebut not limitation, communications network 608 may include wireless orwired communication links, telephone or telecommunications systems,information buses or channels, optical fibers, terrestrial or spacevehicle resources, local area networks, wide area networks, intranets,the Internet, routers or switches, and the like, or any combinationthereof. As illustrated, for example, via a dashed lined box partiallyobscured by third device 606, there may be additional like devicesoperatively coupled to communications network 608. It is also recognizedthat all or part of various devices or networks shown in computingenvironment 600, or processes or methods, as described herein, may beimplemented using or otherwise including hardware, firmware, software,or any combination thereof.

By way of example but not limitation, second device 604 may include atleast one processing unit 610 that may be operatively coupled to amemory 612 via a bus 614. Processing unit 610 may be representative ofone or more circuits capable of performing at least a portion of asuitable computing procedure or process. For example, processing unit610 may include one or more processors, controllers, microprocessors,microcontrollers, application specific integrated circuits, digitalsignal processors, programmable logic devices, field programmable gatearrays, or the like, or any combination thereof.

Memory 612 may be representative of any information storage mechanism orappliance. Memory 612 may include, for example, a primary memory 616 anda secondary memory 618. Primary memory 616 may include, for example, arandom access memory, read only memory, etc. While illustrated in thisexample as being separate from processing unit 610, it should beunderstood that all or part of primary memory 616 may be provided withinor otherwise co-located/coupled with processing unit 610. Secondarymemory 618 may include, for example, same or similar type of memory asprimary memory or one or more information storage devices or systems,such as, for example, a disk drive, an optical disc drive, a tape drive,a solid state memory drive, etc. In certain implementations, secondarymemory 618 may be operatively receptive of, or otherwise configurable tocouple to, a computer-readable medium 620. Computer-readable medium 620may include, for example, any non-transitory storage medium that maycarry or make accessible information, code, or instructions for one ormore of devices in computing environment 600. Computer-readable medium620 may also be referred to as a storage medium.

Second device 604 may include, for example, a communication interface622 that may provide for or otherwise support an operative coupling ofsecond device 604 to at least communications network 608. By way ofexample but not limitation, communication interface 622 may include anetwork interface device or card, a modem, a router, a switch, atransceiver, and the like. Second device 604 may also include, forexample, an input/output device 624. Input/output device 624 may berepresentative of one or more devices or features that may beconfigurable to accept or otherwise introduce human or machine inputs,or one or more devices or features that may be capable of delivering orotherwise providing for human or machine outputs. By way of example butnot limitation, input/output device 624 may include an operativelyconfigured display, speaker, keyboard, mouse, trackball, touch screen,information port, or the like.

Methodologies described herein may be implemented by various meansdepending upon applications according to particular features orexamples. For example, methodologies may be implemented in hardware,firmware, software, discrete/fixed logic circuitry, any combinationthereof, and so forth. In a hardware or logic circuitry implementation,for example, a processing unit may be implemented within one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,electronic devices, other devices or units designed to perform thefunctions described herein, or combinations thereof, just to name a fewexamples.

For a firmware or software implementation, methodologies may beimplemented with modules (e.g., procedures, functions, etc.) havinginstructions that perform functions described herein. Anycomputer-readable medium tangibly embodying instructions may be used inimplementing methodologies described herein. For example, software codesmay be stored in a memory and executed by a processor. Memory may beimplemented within the processor or external to the processor. As usedherein the term “memory” may refer to any type of long term, short term,volatile, non-volatile, or other memory and is not to be limited to anyparticular type of memory or number of memories, or type of media uponwhich memory is stored. In at least some implementations, one or moreportions of the herein described storage media may store signalsrepresentative of information as expressed by a particular state of thestorage media. For example, an electronic signal representative ofinformation may be “stored” in a portion of the storage media (e.g.,memory) by affecting or changing the state of such portions of thestorage media to represent information as binary information (e.g., viaones and zeros). As such, in a particular implementation, such a changeof state of the portion of the storage media to store a signalrepresentative of information constitutes a transformation of storagemedia to a different state or thing.

As was indicated, in one or more example implementations, the functionsdescribed may be implemented in hardware, software, firmware,discrete/fixed logic circuitry, some combination thereof, and so forth.If implemented in software, the functions may be stored on a physicalcomputer-readable medium as one or more instructions or code.Computer-readable media include physical computer storage media. Astorage medium may be any available physical medium that may be accessedby a computer. By way of example, and not limitation, suchcomputer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disc storage, magnetic disk storage or other magnetic storagedevices, or any other medium that may be used to store desired programcode in the form of instructions or information structures and that maybe accessed by a computer or processor thereof. Disk and disc, as usedherein, includes compact disc (CD), laser disc, optical disc, digitalversatile disc (DVD), floppy disk and blue-ray disc where disks usuallyreproduce information magnetically, while discs reproduce informationoptically with lasers.

As discussed above, a mobile device may be capable of communicating withone or more other devices via wireless transmission or receipt ofinformation over various communications networks using one or morewireless communication techniques. Here, for example, wirelesscommunication techniques may be implemented using a wireless wide areanetwork (WWAN), a wireless local area network (WLAN), a wirelesspersonal area network (WPAN), or the like. The term “network” and“system” may be used interchangeably herein. A WWAN may be a CodeDivision Multiple Access (CDMA) network, a Time Division Multiple Access(TDMA) network, a Frequency Division Multiple Access (FDMA) network, anOrthogonal Frequency Division Multiple Access (OFDMA) network, aSingle-Carrier Frequency Division Multiple Access (SC-FDMA) network, aLong Term Evolution (LTE) network, a WiMAX (IEEE 802.16) network, and soon. A CDMA network may implement one or more radio access technologies(RATs) such as cdma2000, Wideband-CDMA (W-CDMA), Time DivisionSynchronous Code Division Multiple Access (TD-SCDMA), to name just a fewradio technologies. Here, cdma2000 may include technologies implementedaccording to IS-95, IS-2000, and IS-856 standards. A TDMA network mayimplement Global System for Mobile Communications (GSM), DigitalAdvanced Mobile Phone System (D-AMPS), or some other RAT. GSM and W-CDMAare described in documents from a consortium named “3rdGenerationPartnership Project” (3GPP). Cdma2000 is described in documents from aconsortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPPand 3GPP2 documents are publicly available. A WLAN may include an IEEE802.11x network, and a WPAN may include a Bluetooth network, an IEEE802.15x, or some other type of network, for example. The techniques mayalso be implemented in conjunction with any combination of WWAN, WLAN,or WPAN. Wireless communication networks may include so-called nextgeneration technologies (e.g., “4G”), such as, for example, Long TermEvolution (LTE), Advanced LTE, WiMAX, Ultra Mobile Broadband (UMB), orthe like.

In an implementation, a mobile device may, for example, be capable ofcommunicating with one or more femtocells, such as for the purpose ofestimating its location, obtaining positioning assistance data,extending cellular telephone service into a business or home, or thelike. As used herein, “femtocell” may refer to one or more smaller-sizecellular base stations that may be capable of detecting a wirelesssignal transmitted from a mobile device using one or more appropriatetechniques. Typically, although not necessarily, a femtocell may utilizeor otherwise be compatible with various types of communicationtechnology such as, for example, Universal Mobile TelecommunicationsSystem (UTMS), Long Term Evolution (LTE), Evolution-Data Optimized orEvolution-Data only (EV-DO), GSM, Worldwide Interoperability forMicrowave Access (WiMAX), Code division multiple access (CDMA)-2000, orTime Division Synchronous Code Division Multiple Access (TD-SCDMA), toname just a few examples among many possible. In certainimplementations, a femtocell may comprise integrated WiFi, for example,and may provide a mobile device access to a larger cellulartelecommunication network by way of another broadband network, such asthe Internet. However, such details relating to femtocells are merelyexamples, and claimed subject matter is not so limited.

Techniques described herein may be used with an SPS that includes anyone of several GNSS or combinations of GNSS. Furthermore, techniques maybe used with positioning systems that utilize terrestrial transmittersacting as “pseudolites”, or a combination of SVs and such terrestrialtransmitters. Terrestrial transmitters may, for example, includeground-based transmitters that broadcast a PN code or other ranging code(e.g., similar to a GPS or CDMA cellular signal, etc.). Such atransmitter may be assigned a unique PN code so as to permitidentification by a remote receiver. Terrestrial transmitters may beuseful, for example, to augment an SPS in situations where SPS signalsfrom an orbiting SV might be unavailable, such as in tunnels, mines,buildings, urban canyons or other enclosed areas. Another implementationof pseudolites is known as radio-beacons. The term “space vehicle” (SV),as used herein, is intended to include terrestrial transmitters actingas pseudolites, equivalents of pseudolites, and possibly others. Theterms “SPS signals” or “SV signals”, as used herein, is intended toinclude SPS-like signals from terrestrial transmitters, includingterrestrial transmitters acting as pseudolites or equivalents ofpseudolites.

Also, computer-readable code or instructions may be transmitted viasignals over physical transmission media from a transmitter to areceiver (e.g., via electrical digital signals). For example, softwaremay be transmitted from a website, server, or other remote source usinga coaxial cable, fiber optic cable, twisted pair, digital subscriberline (DSL), or physical components of wireless technologies such asinfrared, radio, and microwave. Combinations of the above may also beincluded within the scope of physical transmission media. Such computerinstructions may be transmitted in portions (e.g., first and secondportions) at different times (e.g., at first and second times). Someportions of this Detailed Description are presented in terms ofalgorithms or symbolic representations of operations on binary digitalsignals stored within a memory of a specific apparatus or specialpurpose computing device or platform. In the context of this particularSpecification, the term specific apparatus or the like includes ageneral purpose computer once it is programmed to perform particularfunctions pursuant to instructions from program software. Algorithmicdescriptions or symbolic representations are examples of techniques usedby those of ordinary skill in the signal processing or related arts toconvey the substance of their work to others skilled in the art. Analgorithm is here, and generally, considered to be a self-consistentsequence of operations or similar signal processing leading to a desiredresult. In this context, operations or processing involve physicalmanipulation of physical quantities. Typically, although notnecessarily, such quantities may take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, orotherwise manipulated.

It has proven convenient at times, principally for reasons of commonusage, to refer to signals as bits, information, values, elements,symbols, characters, variables, terms, numbers, numerals, or the like.It should be understood, however, that all of these or similar terms areto be associated with appropriate physical quantities and are merelyconvenient labels. Unless specifically stated otherwise, as is apparentfrom the discussion above, it is appreciated that throughout thisSpecification discussions utilizing terms such as “processing,”“computing,” “calculating,” “determining,” “ascertaining,”“identifying,” “associating,” “measuring,” “performing,” or the likerefer to actions or processes of a specific apparatus, such as a specialpurpose computer or a similar special purpose electronic computingdevice. In the context of this Specification, therefore, a specialpurpose computer or a similar special purpose electronic computingdevice is capable of manipulating or transforming signals, typicallyrepresented as physical electronic, electrical, or magnetic quantitieswithin memories, registers, or other information storage devices,transmission devices, or display devices of the special purpose computeror similar special purpose electronic computing device.

Terms, “and” and “or” as used herein, may include a variety of meaningsthat also is expected to depend at least in part upon the context inwhich such terms are used. Typically, “or” if used to associate a list,such as A, B, or C, is intended to mean A, B, and C, here used in theinclusive sense, as well as A, B, or C, here used in the exclusivesense. Reference throughout this specification to “one example” or “anexample” means that a particular feature, structure, or characteristicdescribed in connection with the example is included in at least oneexample of claimed subject matter. Thus, the appearances of the phrase“in one example” or “an example” in various places throughout thisspecification are not necessarily all referring to the same example. Inaddition, the term “one or more” as used herein may be used to describeany feature, structure, or characteristic in the singular or may be usedto describe some combination of features, structures or characteristics.Though, it should be noted that this is merely an illustrative exampleand claimed subject matter is not limited to this example. Furthermore,the particular features, structures, or characteristics may be combinedin one or more examples. Examples described herein may include machines,devices, engines, or apparatuses that operate using digital signals.Such signals may comprise electronic signals, optical signals,electromagnetic signals, or any form of energy that provides informationbetween locations.

While certain example techniques have been described and shown hereinusing various methods or systems, it should be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein. Therefore, it isintended that claimed subject matter not be limited to particularexamples disclosed, but that such claimed subject matter may alsoinclude all implementations falling within the scope of the appendedclaims, and equivalents thereof.

What is claimed is:
 1. A method comprising: obtaining, at a mobiledevice, a rough estimate of a location of said mobile device;identifying a first plurality of transmitters within a first signalacquisition range of said mobile device based, at least in part, onpositioning assistance data obtained for said location; transmittingprobe requests addressed to at least some of said first plurality oftransmitters; selectively initiating a passive scan at a receiver ofsaid mobile device if a number of responses to said probe requestsreceived from said at least some of said first plurality of transmittersis less than a threshold number; determining whether said location ofsaid mobile device has changed; and obtaining new positioning assistancedata based, at least in part, on said determination.
 2. The method ofclaim 1, and further comprising: identifying a second plurality oftransmitters within a second signal acquisition range of said mobiledevice based, at least in part, on said new positioning assistance datafor said changed location.
 3. The method of claim 2, and furthercomprising: transmitting additional probe requests addressed to at leastsome of said second plurality of transmitters; and flagging a venueassociated with said changed location for regeneration or reconstructionof positioning assistance data for said venue if a number of responsesto said additional probe requests received from said at least some ofsaid second plurality of transmitters is less than a threshold number.4. The method of claim 2, wherein said second plurality of transmittersincludes one or more of said first plurality of transmitters.
 5. Themethod of claim 2, wherein one or more of said first plurality oftransmitters and said second plurality of transmitters is associatedwith an indoor environment.
 6. The method of claim 1, wherein saiddetermining whether said location of said mobile device has changed isbased, at least in part, on performing at least one location contextidentifier (LCI) disambiguation operation.
 7. The method of claim 6,wherein said at least one LCI disambiguation operation is implemented todistinguish between a plurality of candidate LCIs covering said roughestimate of said location of said mobile device.
 8. The method of claim7, wherein said plurality of candidate LCIs comprise at least one of thefollowing: a plurality of different floors of a building; a plurality ofdifferent portions of a building; or any combination thereof.
 9. Themethod of claim 6, wherein said at least one LCI disambiguationoperation is based, at least in part, on one or more wireless signalsreceived by said mobile device in connection with said passive scan. 10.The method of claim 6, wherein said at least one LCI disambiguationoperation is based, at least in part, on one or more image featuresextracted from captured images corresponding to particular LCIs of aplurality of candidate LCIs covering said rough estimate of saidlocation of said mobile device.
 11. The method of claim 1, wherein saidat least some of said first plurality of transmitters comprisetransmitters whose one or more expected signal characteristics exceed apredetermined threshold value, said one or more expected signalcharacteristics comprising at least one of the following: a receivedsignal strength-type characteristic; a round-trip delay time-typecharacteristic; or any combination thereof.
 12. The method of claim 1,and further comprising obtaining a position fix of said mobile devicebased, at least in part, on said new positioning assistance data. 13.The method of claim 1, wherein said new positioning assistance compriseat least one of the following: an LCI for said changed location; a radioheat map for said changed location; an electronic digital map for saidchanged location; identities of a second plurality of transmitters;locations of a second plurality of transmitters; a routing graph forsaid changed location; or any combination thereof.
 14. An apparatuscomprising: means for obtaining, at a mobile device, a rough estimate ofa location of said mobile device; means for identifying a firstplurality of transmitters within a first signal acquisition range ofsaid mobile device based, at least in part, on positioning assistancedata obtained for said location; means for transmitting probe requestsaddressed to at least some of said first plurality of transmitters;means for selectively initiating a passive scan at a receiver of saidmobile device if a number of responses to said probe requests receivedfrom said at least some of said first plurality of transmitters is lessthan a threshold number; means for determining whether said location ofsaid mobile device has changed; and means for obtaining new positioningassistance data based, at least in part, on said determination.
 15. Theapparatus of claim 14, and further comprising: means for identifying asecond plurality of transmitters within a second signal acquisitionrange of said mobile device based, at least in part, on said newpositioning assistance data for said changed location.
 16. The apparatusof claim 15, and further comprising: means for transmitting additionalprobe requests addressed to at least some of said second plurality oftransmitters; and means for flagging a venue associated with saidchanged location for regeneration or reconstruction of positioningassistance data for said venue if a number of responses to saidadditional probe requests received from said at least some of saidsecond plurality of transmitters is less than a threshold number. 17.The apparatus of claim 14, wherein said means for determining whethersaid location of said mobile device has changed further comprises meansfor performing at least one location context identifier (LCI)disambiguation operation.
 18. An apparatus comprising: a wirelesstransceiver to communicate with an electronic communications network to:obtain, at a mobile device, a rough estimate of a location of saidmobile device; and one or more processors coupled to a memory, said oneor more processors and said memory configured to: identify a firstplurality of transmitters within a first signal acquisition range ofsaid mobile device based, at least in part, on positioning assistancedata obtained for said location; wherein said wireless transceiverfurther configured to: transmit probe requests addressed to at leastsome of said first plurality of transmitters; and wherein said one ormore processors and said memory further configured to: selectivelyinitiate a passive scan at a receiver of said mobile device if a numberof responses to said probe requests received from said at least some ofsaid first plurality of transmitters is less than a threshold number;determine whether said location of said mobile device has changed; andwherein said wireless transceiver further configured to obtain newpositioning assistance data based, at least in part, on saiddetermination.
 19. The apparatus of claim 18, wherein said one or moreprocessors coupled to said memory further configured to: identify asecond plurality of transmitters within a second signal acquisitionrange of said mobile device based, at least in part, on said newpositioning assistance data for said changed location.
 20. The apparatusof claim 19, wherein said wireless transceiver further configured to:transmit additional probe requests addressed to at least some of saidsecond plurality of transmitters; and wherein said one or moreprocessors and said memory further configured to: flag a venueassociated with said changed location for regeneration or reconstructionof positioning assistance data for said venue if a number of responsesto said additional probe requests received from said at least some ofsaid second plurality of transmitters is less than a threshold number.21. The apparatus of claim 18, wherein said one or more processors andsaid memory further configured to: determine whether said location ofsaid mobile device has changed based, at least in part, on performing atleast one location context identifier (LCI) disambiguation operation.22. The apparatus of claim 21, wherein said at least one LCIdisambiguation operation is implemented to distinguish between aplurality of candidate LCIs covering said rough estimate of saidlocation of said mobile device.
 23. The apparatus of claim 22, whereinsaid plurality of candidate LCIs comprise at least one of the following:a plurality of different floors of a building; a plurality of differentportions of a building; or any combination thereof.
 24. The apparatus ofclaim 21, wherein said at least one LCI disambiguation operation isbased, at least in part, on one or more image features extracted fromcaptured images corresponding to particular LCIs of a plurality ofcandidate LCIs covering said rough estimate of said location of saidmobile device.
 25. The apparatus of claim 21, wherein said at least oneLCI disambiguation operation is based, at least in part, on one or morewireless signals received by said mobile device in connection with saidpassive scan.
 26. The apparatus of claim 18, wherein said at least someof said first plurality of transmitters comprise transmitters whose oneor more expected signal characteristics exceed a predetermined thresholdvalue.
 27. The apparatus of claim 18, wherein said new positioningassistance comprise at least one of the following: an LCI for saidchanged location; a radio heat map for said changed location; anelectronic digital map for said changed location; identities of a secondplurality of transmitters; locations of a second plurality oftransmitters; a routing graph for said changed location; or anycombination thereof.
 28. A non-transitory storage medium havinginstructions executable by a processor to: obtain, at a mobile device, arough estimate of a location of said mobile device; identify a firstplurality of transmitters within a first signal acquisition range ofsaid mobile device based, at least in part, on positioning assistancedata obtained for said location; transmit probe requests addressed to atleast some of said first plurality of transmitters; selectively initiatea passive scan at a receiver of said mobile device if a number ofresponses to said probe requests received from said at least some ofsaid first plurality of transmitters is less than a threshold number;determine whether said location of said mobile device has changed; andobtain new positioning assistance data based, at least in part, on saiddetermination.
 29. The non-transitory storage medium of claim 28,wherein said instructions further comprise instructions to: identify asecond plurality of transmitters within a second signal acquisitionrange of said mobile device based, at least in part, on said newpositioning assistance data for said changed location.
 30. Thenon-transitory storage medium of claim 28, wherein said instructionsfurther comprise instructions to: transmit additional probe requestsaddressed to at least some of said second plurality of transmitters; andflag a venue associated with said changed location for regeneration orreconstruction of positioning assistance data for said venue if a numberof responses to said additional probe requests received from said atleast some of said second plurality of transmitters is less than athreshold number.